Physiological and morphological techniques have provided evidence that there are different classes of cells in the lateral geniculate nucleus of the cat. They are thought to serve different functions in the visual process and their development is affected in diffferent ways by postnatal visual stimulation. Recent evidence suggests that a large cell organell - a cytoplasmic laminated body or CLB - is associated with members of one of the cell types found in lateral geniculate nucleus. The techniques previously used to identify CLBs however greatly restricted the number of cells which can be studied and thus complicates the task of correlating morphologically defined cell types with cell classes based upon electrophysiological data. The present proposal describes a novel procedure for identification of cells containing CLBs which permits extensive, quantitative description of the distribution of neurons containing CLBs throughout both the laminated and the non-laminated regions of the geniculate nucleus. It is thus proposed (1) to examine the distribution of cells containing CLBs in normal adult cats to determine if they can be matched to one of the physiologically demonstrated cell types, (2) to examine the consequences of disrupting normalpostnatal visual exposure on the distribution of cells containing CLBs in the lateral geniculate nucleus and (3) to study the postnatal developmental history of cells containiing this organelle. It is hoped this will enable a correlation between physiological and morphological studies of the cat's visual system.